Wireless messaging method and mobile station

ABSTRACT

A wireless messaging method includes the steps of: when a mobile station is transmitting a message to a network and a first handover occurs, evaluating network conditions to generate an indication signal; and re-transmitting the message according to the indication signal.

BACKGROUND

The present invention relates to a wireless messaging method and amobile station implementing the wireless messaging method, and moreparticularly to a wireless messaging method for transmitting dataaccording to network conditions.

The Short Message Service (SMS) allows messages to be exchanged betweenmobile users and to be broadcasted to all mobile users in a specifiedgeographical area. Messages are sent to a Short Message Service Centre(SMSC) which provides a store-and-forward mechanism. If a recipient of amessage is not reachable, the SMSC queues the message for later retry.An SMS message is sent segment by segment due to the capability of theradio resource management (RR) layer. When a mobile station startssending a message to the SMSC through a base station and a handoveroccurs, the mobile station will stop sending and the network willdiscard the sent segments of the message. At the same time, the mobilestation starts a timer to count until reaching a predetermined time(e.g., 14˜21 seconds, this timer value is not defined in thespecifications 3GPP TS 24.011 version 5.0.0 Release 5 nor 3GPP TS51.010-1 version 5.0.0 Release 5). When the predetermined time is up,the mobile station will resend the whole message to a new base station.When the mobile station resends the message to this new base station andanother handover occurs, the mobile station again terminates the messagesending and retry after counting to the predetermined time. If it isdetermined that the message sending process has failed a few times, itwill stop sending the message and report the failure notification to theuser.

Furthermore, when the mobile station receives a message from the SMSCthrough the base station and a handover occurs before the mobile stationtransmits an acknowledgment signal of the received message, the networkmay try to resend the message to the mobile station since theacknowledgment signal from the mobile station was not received.Consequently, the mobile station will repeatedly receive the samemessage.

SUMMARY

One of the objectives of the present invention is to provide a wirelessmessaging method for transmitting data according to network conditions.

According to a first embodiment of the present invention, a wirelessmessaging method is disclosed. The wireless messaging method comprisesthe steps of: when a mobile station is transmitting a message to anetwork and a first handover occurs, evaluating network conditions togenerate an indication signal; and re-transmitting the message accordingto the indication signal.

According to a second embodiment of the present invention, a wirelessmessaging method is disclosed. The wireless messaging method comprisesthe steps of: when a mobile station receives a message from a networkand a first handover occurs before the mobile station successfullytransmits an acknowledgment signal of the received message, evaluatingnetwork conditions to generate an indication signal; and transmittingthe acknowledgment signal according to the indication signal.

According to a third embodiment of the present invention, a mobilestation is disclosed. The mobile station comprises a transceiver, aradio resource management sublayer, and a short message call managementsublayer. The transceiver is arranged for transmitting and receivingsignals. The radio resource management sublayer is arranged forevaluating network conditions to generate an indication signal when thetransceiver is transmitting a message while a first handover occurs. Theshort message call management sublayer is arranged for directing thetransceiver to re-transmit the message according to the indicationsignal generated in the radio resource management sublayer.

According to a fourth embodiment of the present invention, a mobilestation is disclosed. The mobile station comprises a transceiver, aradio resource management sublayer, and a short message call managementsublayer. The transceiver is arranged for transmitting and receivingcommunication signals. The radio resource management sublayer isarranged for evaluating network conditions to generate an indicationsignal when the transceiver receives a message and a first handoveroccurs before the transceiver transmits an acknowledgment signal of thereceived message. The short message call management sublayer is arrangedfor directing the transceiver to transmit the acknowledgment signalaccording to the indication signal generated by the radio resourcemanagement sublayer.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a wireless messaging method accordingto a first embodiment of the present invention.

FIG. 2 is a flowchart illustrating a method of evaluating networkconditions of a mobile station according to an embodiment of the presentinvention.

FIG. 3 is a flowchart illustrating a method of determining power of asignal received from the current base station to evaluate theprobability of occurrence of a second handover according to anembodiment of the present invention.

FIG. 4 is a flowchart illustrating a method of comparing powers of thesignal received from the current base station and the signal receivedfrom a neighboring base station to evaluate the probability ofoccurrence of a second handover according to an embodiment of thepresent invention.

FIG. 5 is a flowchart illustrating a method of determining a servingcell quality of a current serving cell to evaluate the probability ofoccurrence of a second handover according to an embodiment of thepresent invention.

FIG. 6 is a flowchart illustrating a method of evaluating the networkcondition according to another embodiment of the present invention.

FIG. 7 is a diagram illustrating the wireless messaging method accordingto a second embodiment of the present invention.

DETAILED DESCRIPTION

Certain terms are used throughout the description and following claimsto refer to particular components. As one skilled in the art willappreciate, electronic equipment manufacturers may refer to a componentby different names. This document does not intend to distinguish betweencomponents that differ in name but not function. In the followingdescription and in the claims, the terms “include” and “comprise” areused in an open-ended fashion, and thus should be interpreted to mean“include, but not limited to . . . ”. Also, the term “couple” isintended to mean either an indirect or direct electrical connection.Accordingly, if one device is coupled to another device, that connectionmay be through a direct electrical connection, or through an indirectelectrical connection via other devices and connections.

In this document, the terminologies used are for GSM (Global System forMobile) network system, such as mobile station and base station;however, this invention shall not be limited to GSM network system. Thewireless messaging method and handheld devices implementing the methodof the present invention can be applied in other network systems such asUMTS (Universal Mobile Telecommunication system) and LTE (Long TermEvolution). The mobile station thus represents any handheld devices witha transceiver capable of communicating with a wireless network, and thebase station represents any wireless communication station in thewireless network such as Node B or eNode B.

Please refer to FIG. 1. FIG. 1 is a diagram illustrating a wirelessmessaging method 100 according to an embodiment of the presentinvention. In this embodiment, the wireless messaging method 100 isemployed in a mobile station, and the wireless messaging method 100 is amobile originating (MO) case. The third layer of the GSM networkcommunication protocol is divided into sublayers, including CM (CallManagement), MM (Mobility Management), and RR (Radio ResourceManagement). Sublayers are responsible for different functions. Toperform a function supported by the GSM network, such as making a phonecall or sending an SMS message, an upper sublayer issues a command toinform a lower sublayer to transmit signals accordingly. RR sublayer isresponsible for maintaining connections between the mobile station andBase Station Controller (BSC) and establishing or releasing ofcommunication channels, and it is also responsible for radio managementsuch as power control, discontinuous transmission, timing advance forsignal transmission, and handover. MM sublayer is responsible formobility management so that the current location of the mobile stationis known to the GSM network, it is also responsible for authenticationand ciphering. CM sublayer is responsible for call control, such asestablishing or release of a call, and selection of voice or faxcommunication. CM is also responsible for supplementary service (SS)management and SMS management. As shown in FIG. 1, SM-CM is the CMsublayer responsible for SMS management.

According to the wireless messaging method 100, the RR sublayerevaluates network conditions of the mobile station to generate anindication Sid when an SMS message transmission is failed due to anevent such as handover or assignment. The SM-CM sublayer issues acommand to request for message re-transmission according to theindication Sid.

In FIG. 1, the SM-CM sublayer receives a request (i.e., SMCP_EST_REQ)when the user wishes to send a message (i.e., RP-DATA) through thenetwork. The SM-CM sublayer sends a short-message-establish request(MMSMS_EST_REQ) to the MM sublayer. Then, the MM replies with aconfirmation (i.e., MMSMS_EST_CNF) to the SM-CM sublayer if theconnection is established. When the SM-CM sublayer receives theMMSMS_EST_CNF, the SM-CM sublayer sends a data request (i.e.,MMSMS_DATA_REQ) to the MM sublayer in order to request the MM sublayerto send CP-DATA on the established connection. Then, the MM sublayertransfers the CP-DATA to the RR sublayer, and the RR sublayer transmitsthe message to the network by radio signal.

When the RR sublayer transmits the message to the SMSC through a basestation and a first handover occurs, the RR sublayer terminates themessage transmission. Then, the RR sublayer evaluates network conditionsof the mobile station to generate the indication Sid to the SM-CMsublayer. For example, when the first handover is complete, the RRsublayer evaluates the network conditions between the mobile station andthe base station to determine if the network conditions are good enoughto re-transmit the message. In other words, the RR sublayer evaluatesthe network conditions between the mobile station and the base stationto generate an evaluation result. The RR sublayer generates anindication Sid to the SM-CM sublayer based on the evaluation result. Inone embodiment, if the evaluation result indicates that the networkconditions are good enough, the RR sublayer sends the indication Sid tothe SM-CM sublayer to indicate the SM-CM sublayer can re-transmit themessage immediately. Otherwise, the RR sublayer will not generate theindication Sid, and continues to evaluate the network conditions untilthe network conditions are good enough for re-transmission of themessage. Furthermore, the SM-CM sublayer may stop a retry timer when theindication Sid is generated, wherein the retry timer starts countingwhen the first handover occurs. In another embodiment, the RR sublayergenerates an indication Sid indicating the network conditions for theSM-CM sublayer to determine the re-transmission method. For example, theSM-CM sublayer determines whether to re-transmit the messageimmediately, or to send the message with best effort, or to keep relyingon the timer for re-transmission according to the indication Sid.Compared to the related art, the present embodiment re-transmits theterminated message according to the network conditions rather thancounting a fixed period by the retry timer.

Please refer to FIG. 2. FIG. 2 is a flowchart illustrating a method 200of evaluating the network conditions of the mobile station to determinewhether to re-transmit the message immediately according to anembodiment of the present invention. Provided that substantially thesame result is achieved, the steps of the flowchart shown in FIG. 2 neednot be in the exact order shown and need not be contiguous; that is,other steps can be intermediate. The method 200 comprises the followingsteps:

Step 201: Determine if the first handover is accomplished;

Step 202: When the first handover is accomplished, determine if thecomplete message is transmitted successfully;

Step 203: When the message is not transmitted completely, evaluate aprobability of occurrence of a second handover upon the mobile station;if the probability is smaller than a criterion, go to step 204, if theprobability is not smaller than the criterion, go to step 205;

Step 204: Re-transmit the message immediately;

Step 205: Wait for a retry timer for re-transmission.

When the first handover is accomplished but the message is nottransmitted to the base station successfully, the mobile stationevaluates the probability of occurrence of a second handover upon themobile station according to a criterion, wherein the criterion is apredetermined threshold value indicating the probability of theoccurrence of the second handover after the first handover. When theprobability of occurrence is smaller than the criterion, indicating thepath (i.e., the network conditions) between the mobile station and thecurrent base station is relatively stable, the mobile stationre-transmits the message immediately. Otherwise, the mobile station doesnot re-transmit the message immediately. Please note that, according tothe embodiments of the present invention, there are several methods forevaluating the network conditions of the mobile station. According to anembodiment, the RR sublayer determines power of a signal received from acurrent base station to evaluate the probability of occurrence of thesecond handover as shown in FIG. 3. FIG. 3 is a flowchart illustrating amethod 300 of determining the power of the signal received from thecurrent base station to evaluate the probability of occurrence of thesecond handover according to an embodiment of the present invention.Provided that substantially the same result is achieved, the steps ofthe flowchart shown in FIG. 3 need not be in the exact order shown andneed not be contiguous; that is, other steps can be intermediate.Furthermore, it should be noted that the current serving cell is aserving cell corresponding to the mobile station when the first handoveris accomplished. The method 300 comprises the following steps:

Step 301: Determine if the power of the signal received from the currentbase station corresponding to the current serving cell is greater than apredetermined power threshold; when the power of the signal receivedfrom the current base station is greater than the predetermined powerthreshold, go to step 302, and when the power of the signal receivedfrom the current base station is not greater than the predeterminedpower threshold, go to step 304;

Step 302: Determine that the probability of occurrence of the secondhandover is smaller than the criterion;

Step 303: Re-transmit the message immediately;

Step 304: Determine that the probability of occurrence of the secondhandover is not smaller than the criterion;

Step 305: Do not re-transmit the message immediately.

When the power of the signal received from the current base station isgreater than the predetermined power threshold, this means the mobilestation may be close to the current base station, and the networkconditions are good enough to re-transmit the message to the currentbase station. In this case, the mobile station re-transmits the messageimmediately. Otherwise, the mobile station will not re-transmit themessage immediately. According to another embodiment, the RR sublayercompares the power of the signal received from the current base stationcorresponding to the current serving cell and the power of the signalreceived from one or more neighboring base station(s) to evaluate theprobability of occurrence of the second handover as shown in FIG. 4.FIG. 4 is a flowchart illustrating a method 400 of comparing the ratioof powers of the signal received from the current base station and theneighboring base station to evaluate the probability of occurrence ofthe second handover according to an embodiment of the present invention.Provided that substantially the same result is achieved, the steps ofthe flowchart shown in FIG. 4 need not be in the exact order shown andneed not be contiguous; that is, other steps can be intermediate.Furthermore, it should be noted that the current serving cell is aserving cell corresponding to the mobile station when the first handoveris accomplished. The method 400 comprises the following steps:

Step 401: Determine if a ratio of the power of the signal received fromthe current base station to the power of the signal received from theneighboring base station is greater than a threshold; when the ratio isgreater than the threshold, go to step 402, and when the ratio is notgreater than the threshold, go to step 404;

Step 402: Determine that the probability of occurrence of the secondhandover is smaller than the criterion;

Step 403: Re-transmit the message immediately;

Step 404: Determine that the probability of occurrence of the secondhandover is not smaller than the criterion;

Step 405: Do not re-transmit the message immediately.

Similarly, when the power of the signal received from the current basestation is much greater than the power of the signal received from anyof the neighboring base stations (e.g., the power of the signal receivedfrom the current base station is 10 dB larger than the power of thesignal received from the closest neighboring base station), this meansthe network conditions are good enough to re-transmit the message to thecurrent base station. In this case the RR sublayer generates and sendsthe indication Sid to the SM-CM sublayer, and the SM-CM determines tore-transmit the message immediately. According to another embodiment, aserving cell quality of the current serving cell is compared to apredetermined quality threshold to evaluate the probability ofoccurrence of the second handover as shown in FIG. 5. FIG. 5 is aflowchart illustrating a method 500 of determining the serving cellquality of the current serving cell to evaluate the probability ofoccurrence of the second handover according to an embodiment of thepresent invention. Provided that substantially the same result isachieved, the steps of the flowchart shown in FIG. 5 need not be in theexact order shown and need not be contiguous; that is, other steps canbe intermediate. Furthermore, it should be noted that the currentserving cell is a serving cell corresponding to the mobile station whenthe first handover is accomplished. The method 500 comprises thefollowing steps:

Step 501: Determine if the serving cell quality of the current servingcell is higher than the predetermined quality threshold; when theserving cell quality of the current serving cell is higher than thepredetermined quality threshold, go to step 502, and when the servingcell quality of the current serving cell is lower than the predeterminedquality threshold, go to step 504;

Step 502: Determine that the probability of occurrence of the secondhandover is higher than the criterion;

Step 503: Re-transmit the message immediately;

Step 504: Determine that the probability of occurrence of the secondhandover is smaller than the criterion;

Step 505: Do not re-transmit the message immediately.

When the serving cell quality of the current serving cell is higher thanthe predetermined quality threshold (e.g., 3), this means the pathbetween the mobile station and the current base station may berelatively clean or stable, and the network conditions are good enoughto re-transmit the message to the base station. In this case the RRsublayer generates and sends the indication Sid to the SM-CM sublayer,and the SM-CM sublayer directs the transceiver to re-transmit themessage immediately. Beside to the embodiments shown in FIG. 3, FIG. 4,FIG. 5, the mobile station may determine the network conditions bydetecting the movement or mobility of the mobile station, for example,by detecting the speed or velocity of the mobile station to judgewhether it is stationary, slow movement, or rapid movement. In anembodiment, when the mobile station is judged as stationary, the networkconditions are deemed to be stable, and it has a higher probability ofsuccess that the currently-re-transmit-message can be delivered to thebase station. In this case, the mobile station can re-transmit themessage immediately instead of waiting for the retry timer.

Please note that the present invention is not limited to implementingmethods 300, 400, 500, and the movement or mobility detection methodindependently, it is possible to evaluate the network conditions byconsidering the judgments or evaluation outcomes of more than two kindsof methods. Furthermore, it should be noted that the first handover andthe second handover may be one of an intra-cell handover, an inter-cellhandover, an external handover, and a channel assignment.

FIG. 6 shows an embodiment of network condition evaluation method 600considering more than two kinds of judgments or evaluation outcomes.Provided that substantially the same result is achieved, the steps ofthe flowchart shown in FIG. 6 need not be in the exact order shown andneed not be contiguous; that is, other steps can be intermediate. Themethod 600 comprises the following steps:

Step 601: Determine if the mobile station is currently under a movingstatus; if yes go to step 602, if no go to step 606;

Step 602: Evaluate the probability of occurrence of the second handover;when the probability of occurrence of the second handover is smallerthan the criterion, go to step 603, and when the probability ofoccurrence of the second handover is not smaller than the criterion, goto step 605;

Step 603: Determine a size of the message; when the size of the messageis smaller than a first predetermined size threshold, go to step 604,and when the size of the message is not smaller than the firstpredetermined size threshold, go to step 605;

Step 604: Re-transmit the message immediately;

Step 605: Do not re-transmit the message immediately;

Step 606: Evaluate the probability of occurrence of the second handover;when the probability of occurrence of the second handover is smallerthan the criterion, go to step 604, and when the probability ofoccurrence of the second handover is not smaller than the criterion, goto step 607;

Step 607: Determine the size of the message; when the size of themessage is smaller than a second predetermined size threshold, go tostep 604, and when the size of the message is not smaller than thesecond predetermined size threshold, go to step 605.

In step 601, when the variation of power of the signal received from thecurrent base station and the signal received from the neighboring basestation is relatively stable in a predetermined time (e.g., 5 seconds),a first result is generated to indicate that the status of the mobilestation is stationary. Otherwise, the first result indicates that thestatus of the mobile station is moving. In step 602, the above-mentionedmethods 300, 400, 500 may be implemented for evaluating the probabilityof occurrence of the second handover to generate a second result. Whenthe mobile station is under the moving status and the second resultindicates that the probability of occurrence of the second handover islower than the criterion, the indication Sid may indicate the SM-CMsublayer to re-transmit the message with best effort, for example, whenthe size of the message is smaller than a first predetermined sizethreshold, the SM-CM directs the transceiver to re-transmit the messageimmediately.

When the mobile station is under the stationary status (step 606), theabove-mentioned methods 300, 400, 500 may be implemented for evaluatingthe probability of occurrence of the second handover to generate thesecond result. When the second result indicates that the probability ofoccurrence of the second handover is lower than the criterion, the RRsublayer generates the indication Sid to the SM-CM sublayer indicatingthe message can be re-transmitted immediately (step 604). Otherwise, theindication Sid indicates that the message can be transmitted with besteffort, for example, mobile station determines the size of the message(step 607), and when the size of the message is smaller than a secondpredetermined size threshold, the SM-CM sublayer indicating the messagecan be re-transmitted immediately, and when the size of the message islarger than the second predetermined size threshold, the re-transmissionis halted. Normally, the first predetermined size threshold is smallerthan the second predetermined size threshold.

Therefore, when the SM-CM sublayer receives the indication Sidindicating the network conditions are good enough, it sends theMMSMS_DATA_REQ to the MM sublayer to request the MM sublayer to send themessage (i.e., CP-DATA) again.

Please refer to FIG. 7. FIG. 7 is a diagram illustrating a wirelessmessaging method 700 according to another embodiment of the presentinvention. The wireless messaging method 700 is employed in the mobilestation as mentioned in FIG. 1, and the wireless messaging method 700 isa mobile terminating (MT) case. According to the wireless messagingmethod 700, the RR sublayer evaluates the network NW conditions togenerate an indication Sid' when the mobile station receives a messageand a first handover occurs before the mobile station transmits anacknowledgment signal Sack of the received message to the SMSC through abase station. The SM-CM sublayer transmits the acknowledgment signalSack to the base station according to the indication Sid'.

In FIG. 7, when the SM-CM sublayer receives an indication (i.e.,MMSMS_EST_IND) from the MM sublayer, the MMSMS_EST_IND indicates to theSM-CM sublayer that the message (i.e., RP-DATA) from the base station iscomplete. Then, the SM-CM sublayer sends the short-message-establishrequest (MMSMS_EST_REQ) to the MM sublayer, in which the MMSMS_EST_REQcontains the acknowledgment signal Sack (i.e., CP-ACK). Then, the MMsublayer transfers the acknowledgment signal Sack to the RR sublayer,and the MM sublayer transmits the acknowledgment signal Sack to thenetwork NW by a radio signal.

When the RR sublayer transmits the acknowledgment signal Sack to thebase station and the first handover occurs, the RR sublayer terminatesthe transmission. Then, the RR sublayer evaluates network conditions togenerate the indication Sid' to the SM-CM sublayer. More specifically,when the first handover is over, the RR sublayer evaluates the networkconditions to determine if the network conditions are good enough tore-transmit the acknowledgment signal Sack. In other words, the RRsublayer evaluates the network conditions to generate an evaluationresult. In one embodiment, the RR sublayer selectively generates theindication Sid' to the SM-CM sublayer according to the networkconditions. If the evaluation result indicates that the networkconditions are good enough, the RR sublayer sends the indication Sid' tothe SM-CM sublayer to indicate the SM-CM sublayer to re-transmit theterminated acknowledgment signal Sack. Otherwise, the RR sublayer willnot generate the indication Sid', and continues to evaluate the networkconditions until the network conditions are good enough forre-transmitting the acknowledgment signal Sack. In another embodiment,the RR sublayer forwards the network conditions by the indication Sid'to the SM-CM sublayer, and the SM-CM sublayer determines whether totransmit the acknowledgement immediately or to wait till the retry timerexpired. Similar to the wireless messaging method 100, the method 200shown in FIG. 2 may be implemented for evaluating the network conditionsof the mobile station to determine the re-transmission timing.Furthermore, the methods 300, 400, 500 shown in FIGS. 3, 4, 5,respectively, may be utilized for evaluating the probability ofoccurrence of a second handover upon the mobile station when theacknowledgment signal Sack is not successfully transmitted to the basestation. Please note that those skilled in this art will readilyunderstand the operation of the wireless messaging method 700 afterreading the disclosure related to the wireless messaging method 100,thus the detailed description is omitted here for brevity. When theshort message service SMS receives the indication Sid', the SM-CMsublayer sends the MMSMS_DATA_REQ to the MM sublayer to request the MMsublayer to send the acknowledgment signal Sack again.

Briefly, the conventional art may miss the opportunity to re-transmitthe message and the acknowledgment signal Sack as it only relies on aretry timer and re-transmits after a predetermined period. However, byutilizing the wireless messaging methods 100 and 700, the mobile stationre-transmits the message and the acknowledgment signal Sack right afterthe first handover is over if the network conditions are determined goodenough for transmission. Therefore, the present mobile station possesseshigh efficiency of transmitting/receiving a message from the SMSCthrough a base station.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention.

1. A wireless messaging method, comprising: evaluating networkconditions to generate an indication signal when a message istransmitted while a first handover occurs; and re-transmitting themessage according to the indication signal.
 2. The method of claim 1,wherein the step of evaluating the network conditions to generate theindication comprises: evaluating the network conditions in a radioresource management sublayer to generate an evaluation result; andreferring to the evaluation result for generating the indication signalto a short message service call management sublayer.
 3. The method ofclaim 1, wherein the first handover is one of an intra-cell handover, aninter-cell handover, an external handover, and a channel assignment. 4.The method of claim 1, further comprising: stopping a timer according tothe indication signal; wherein the timer starts counting when the firsthandover occurs.
 5. The method of claim 1, wherein the step ofre-transmitting the message according to the indication signal,comprises: determining if the first handover is accomplished; when thefirst handover is accomplished, determining if the message istransmitted successfully; evaluating a probability of occurrence of asecond handover according to the indication signal when the message isnot transmitted successfully; and re-transmitting the message accordingto the probability of occurrence of the second handover.
 6. The methodof claim 5, wherein when the first handover is accomplished, the step ofevaluating the probability of occurrence of the second handovercomprises: determining if power of a signal received from a current basestation is greater than a predetermined power threshold; and when thepower of the signal received from the current base station is greaterthan the predetermined power threshold, determining that the probabilityof occurrence of the second handover is lower than a criterion.
 7. Themethod of claim 5, wherein when the first handover is accomplished, thestep of evaluating the probability of occurrence of the second handovercomprises: determining if a ratio of power of a signal received from acurrent base station to power of a signal received from a neighboringbase station is higher than a threshold; and when the ratio is higherthan the threshold, determining that the probability of occurrence ofthe second handover is lower than a criterion.
 8. The method of claim 5,wherein when the first handover is accomplished, the step of evaluatingthe probability of occurrence of the second handover comprises:determining if a serving cell quality of a current serving cell is lowerthan a predetermined quality threshold; and when the serving cellquality of the current serving cell is lower than the predeterminedquality threshold, determining that the probability of occurrence of thesecond handover is lower than a criterion.
 9. The method of claim 1,further comprising: determining if the first handover is accomplished;when the first handover is accomplished, determining if the message istransmitted successfully; when the message is not transmittedsuccessfully, evaluating a probability of occurrence of a secondhandover according to the indication signal to generate a first result,and determining if it is under a moving status to generate a secondresult; and re-transmitting the message according to the first resultand the second result.
 10. The method of claim 9, wherein the step ofretransmitting the message according to the first result and the secondresult comprises: when the first result shows the probability ofoccurrence of the second handover is lower than a criterion, and thesecond result shows not under the moving status, re-transmitting themessage immediately; when the first result shows the probability ofoccurrence of the second handover is not lower than the criterion, andthe second result shows not under the moving status, determining a sizeof the message, and re-transmitting the message according to the size ofthe message and a first predetermined size threshold; and when the firstresult shows the probability of occurrence of the second handover islower than the criterion, and the second result shows under the movingstatus, determining the size of the message, and re-transmitting themessage according to the size of the message and a second predeterminedsize threshold.
 11. The method of claim 10, wherein: the step ofre-transmitting the message according to the size of the message and thefirst predetermined size threshold comprises: when the size of themessage is smaller than the first predetermined size threshold,re-transmitting the message immediately; and the step of re-transmittingthe message according to the size of the message and the secondpredetermined size threshold comprises: when the size of the message issmaller than the second predetermined size threshold, re-transmittingthe message immediately.
 12. The method of claim 9, wherein the step ofevaluating the probability of occurrence of the second handovercomprises: determining if power of a signal received from a current basestation is greater than a predetermined power threshold; and when thepower of the signal received from the current base station is greaterthan the predetermined power threshold, determining that the probabilityof occurrence of the second handover is lower than a criterion.
 13. Themethod of claim 9, wherein the step of evaluating the probability ofoccurrence of the second handover comprises: determining if a ratio ofpower of a signal received from a current base station to power of asignal received from a neighboring base station is higher than athreshold; and when the ratio is higher than the threshold, determiningthat the probability of occurrence of the second handover is lower thana criterion.
 14. The method of claim 9, wherein the step of evaluatingthe probability of occurrence of the second handover comprises:determining if a serving cell quality is higher than a predeterminedquality threshold; and when the serving cell quality is higher than thepredetermined quality threshold, determining that the probability ofoccurrence of the second handover is lower than a criterion.
 15. Awireless messaging method, comprising: when a mobile station receives amessage from a network and a first handover occurs before the mobilestation successfully transmits an acknowledgment signal of the receivedmessage, evaluating network conditions to generate an indication signal;and transmitting the acknowledgment signal according to the indicationsignal.
 16. The method of claim 15, wherein the step of evaluating thenetwork conditions to generate the indication signal comprises:evaluating the network conditions in a radio resource managementsublayer to generate an evaluation result; and referring to theevaluation result for generating the indication signal to a shortmessage service call management sublayer.
 17. The method of claim 15,wherein the step of transmitting the acknowledgment signal according tothe indication signal comprises: determining if the first handover isaccomplished; when the first handover is accomplished, determining ifthe acknowledgment signal is transmitted successfully; when theacknowledgment signal is not transmitted successfully, evaluating aprobability of occurrence of a second handover upon the mobile station;and re-transmitting the acknowledgment signal according to theprobability of occurrence of the second handover.
 18. The method ofclaim 17, wherein the step of evaluating the probability of occurrenceof the second handover upon the mobile station comprises: determining ifpower of a signal received from a current base station is greater than apredetermined power threshold; and when the power of the signal receivedfrom the current base station is greater than the predetermined powerthreshold, determining that the probability of occurrence of the secondhandover is lower than a criterion.
 19. The method of claim 17, whereinthe step of evaluating the probability of occurrence of the secondhandover upon the mobile station comprises: determining if a ratio ofpower of a signal received from a current base station to power of asignal received from a neighboring base station is higher than athreshold; and when the ratio is higher than the threshold, determiningthat the probability of occurrence of the second handover is lower thana criterion.
 20. The method of claim 17, wherein the step of evaluatingthe probability of occurrence of the second handover upon the mobilestation comprises: determining if a serving cell quality is higher thana predetermined quality threshold; and when the serving cell quality ofthe current serving cell is higher than the predetermined qualitythreshold, determining that the probability of occurrence of the secondhandover is lower than a criterion.
 21. The method of claim 15, furthercomprises: determining if the first handover is accomplished; when thefirst handover is accomplished, determining if the acknowledgment signalis transmitted successfully; when the acknowledgment signal is nottransmitted to the network successfully, evaluating a probability ofoccurrence of a second handover according to the indication signal togenerate a first result, and determining if the mobile station iscurrently under a moving status to generate a second result; andtransmitting the acknowledgment signal according to the first result andthe second result.
 22. A mobile station, comprising: a transceiver, fortransmitting and receiving signals; a radio resource managementsublayer, for evaluating network conditions to generate an indicationsignal when the transceiver is transmitting a message while a firsthandover occurs; and a short message call management sublayer, fordirecting the transceiver to re-transmit the message according to theindication signal generated in the radio resource management sublayer.23. The mobile station of claim 22, wherein the short message callmanagement sublayer directs the transceiver to re-transmit the messageaccording to the indication signal and a size of the message.
 24. Amobile station, comprising: a transceiver, for transmitting andreceiving communication signals; a radio resource management sublayer,for evaluating network conditions to generate an indication signal whenthe transceiver receives a message and a first handover occurs beforethe transceiver transmits an acknowledgment signal of the receivedmessage; and a short message call management sublayer, for directing thetransceiver to transmit the acknowledgment signal according to theindication signal generated by the radio resource management sublayer.